{"id":"CVE-2026-81558","kind":"vulnerability","aliases":["CVE-2026-81558"],"related":[],"title":"Synology DSM: SocketIO API lets logged-in users write specific files","description":"A missing authorization vulnerability in the SocketIo API in Synology DiskStation Manager (DSM) before 7.3.2-86009-5 and 7.4.1-90080-1 allows remote authenticated users to write specific files.","summary":"Synology DiskStation Manager has a missing authorization check in its SocketIO API. A remote user who already has an account can write specific files they should not be able to change.","severity":"medium","cvss":4.3,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["dsm","infrastructure","nas","self-hosted","synology"],"not_affected_if":["patched-dsm","unauthenticated-only-access"],"how_to_check":"- Check the installed DSM version in Control Panel > Info Center; the sources do not give a command.\n- Compare it against the fixed versions listed below.","fix":"- DSM `7.3.2-86009-5` or later on the 7.3 branch\n- DSM `7.4.1-90080-1` or later on the 7.4 branch","status":"open","published_at":"2026-11-12T04:17:20+00:00","first_seen_at":"2026-11-12T04:47:09+00:00","triaged_at":"2026-11-12T04:48:03+00:00","updated_at":"2026-11-12T04:48:03+00:00","category":"infrastructure","confidence":0.7,"triage":{"at":"2026-11-12T04:48:03Z","model":"claude-haiku-5-5","output":{"fix":"- DSM `7.3.2-86009-5` or later on the 7.3 branch\n- DSM `7.4.1-90080-1` or later on the 7.4 branch","reach":"network","title":"Synology DSM: SocketIO API lets logged-in users write specific files","impact":"medium","summary":"Synology DiskStation Manager has a missing authorization check in its SocketIO API. A remote user who already has an account can write specific files they should not be able to change.","audience":"businesses","category":"infrastructure","nicknames":[],"who_cares":["synology","dsm","self-hosted","nas"],"confidence":0.7,"fix_status":"available","needs_auth":"yes","worst_case":"authenticated user writes files they should not change","analyst_note":"Product name in the title is DSM; no product list was given, so the affected range comes only from the description.","how_to_check":"- Check the installed DSM version in Control Panel > Info Center; the sources do not give a command.\n- Compare it against the fixed versions listed below.","plain_action":"","product_name":"","needs_analyst":false,"not_affected_if":["unauthenticated-only-access","patched-dsm"],"who_is_affected":"Synology NAS devices running DSM before 7.3.2-86009-5 or 7.4.1-90080-1 are exposed, and only to users who already have a valid DSM account. Systems on managed or non-Synology hardware are not affected.","user_interaction":"no","product_ecosystem":"","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.000713,"input_tokens":4542,"output_tokens":517,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-1':77C '-2026':14A,17A '-5':73C '-81558':15A,18A '-86009':72C '-90080':76C '7.3.2':71C '7.4.1':75C 'abl':54B 'account':45B 'allow':78C 'alreadi':42B 'api':4A,37B,64C 'authent':80C 'author':32B,59C 'chang':56B 'check':33B 'cve':13A,16A 'diskstat':27B,67C 'dsm':2A,19B,69C 'file':12A,49B,85C 'host':24B 'infrastructur':20B 'let':5A 'log':7A 'logged-in':6A 'manag':28B,68C 'miss':31B,58C 'nas':21B 'remot':39B,79C 'self':23B 'self-host':22B 'socketio':3A,36B,63C 'specif':11A,48B,84C 'synolog':1A,25B,26B,66C 'user':9A,40B,81C 'vulner':60C 'write':10A,47B,83C","nicknames":[],"mitigations":[],"who_affected":"Synology NAS devices running DSM before 7.3.2-86009-5 or 7.4.1-90080-1 are exposed, and only to users who already have a valid DSM account. Systems on managed or non-Synology hardware are not affected.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["dsm","infrastructure","medium","nas","selfhosted","synology"],"campaign_type":null,"search_a":"'-2026':14A,17A '-81558':15A,18A 'api':4A 'cve':13A,16A 'dsm':2A 'file':12A 'let':5A 'log':7A 'logged-in':6A 'socketio':3A 'specif':11A 'synolog':1A 'user':9A 'write':10A","search_b":"'abl':54B 'account':45B 'alreadi':42B 'api':37B 'author':32B 'chang':56B 'check':33B 'diskstat':27B 'dsm':19B 'file':49B 'host':24B 'infrastructur':20B 'manag':28B 'miss':31B 'nas':21B 'remot':39B 'self':23B 'self-host':22B 'socketio':36B 'specif':48B 'synolog':25B,26B 'user':40B 'write':47B","search_c":"'-1':77C '-5':73C '-86009':72C '-90080':76C '7.3.2':71C '7.4.1':75C 'allow':78C 'api':64C 'authent':80C 'author':59C 'diskstat':67C 'dsm':69C 'file':85C 'manag':68C 'miss':58C 'remot':79C 'socketio':63C 'specif':84C 'synolog':66C 'user':81C 'vulner':60C 'write':83C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-12T04:17:20+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N","cvss_by":"security@synology.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-81558","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81558","severity":null,"published_at":"2026-11-12T04:17:20+00:00","modified_at":"2026-11-12T04:17:20+00:00","first_seen_at":"2026-11-12T04:47:09+00:00","fetched_at":"2026-11-12T04:47:09+00:00","note":null}],"documents":[],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}